This invention relates to a fan clutch drive for a vehicle engine.
Because of the high cost of fuel, and because of governmental noise regulations, it is desirable to provide a fan clutch which disconnects the engine cooling fan when its cooling effect is not necessary, and which connects the fan for operation by the vehicle engine when the engine temperature raises to a point that the cooling effect of the fan is necessary. In many vehicles, the cooling effect of the engine fan is necessary during less than ten percent of the time that the vehicle is operated. When the fan is powered when its cooling effect is not necessary, the power necessary to drive the fan is wasted, thereby increasing fuel consumption. Furthermore, engine cooling fans are inherently noisy, and by disconnecting the fan when it is not necessary, the operating conditions of the vehicle may be quieted. One type of fan clutch which has been highly successful with heavy duty vehicles having air brakes is the clutch disclosed in U.S. Pat. No. 3,985,214, owned by assignee of the present invention. However, this fan clutch design is not compatible with smaller vehicles which do not have air brakes, and which are usually provided with direct driven fans. Typical examples of the type of engines in which a fan clutch made pursuant to the teachings of the present invention may be used are trucks having medium-sized gasoline engines or small diesel engines.